JP7176850B2 - Sea-island composite fiber bundle - Google Patents

Description

TECHNICAL FIELD The present invention relates to a sea-island composite fiber bundle, and more particularly to a sea-island composite fiber bundle having a small island diameter. More specifically, it relates to a sea-island type composite fiber bundle capable of stably producing a group of polyphenylene sulfide ultrafine fibers having excellent properties such as high strength and low shrinkage rate, little occurrence of fluff, and excellent quality and grade. is.

BACKGROUND ART Conventionally, ultrafine fibers (microfibers) have been used in industrial materials such as clothing fabrics, artificial leathers, and filters in order to develop flexibility, aesthetics, and denseness.
In recent years, ultrafine fibers (nanofibers) having a single filament diameter of 1 micrometer or less have been proposed in pursuit of delicate touch and softness.

In addition to the ultimate soft touch by scaling down the fiber diameter, nanofibers have been recognized to have the unique effect of nanosize due to the dramatic increase in the specific surface area and porosity of the fiber group. It has potential for product development, and early research, development, and stable production are required.

For example, by using 5-sodium sulfoisophthalic acid and polyethylene glycol copolymerized polyester as the readily soluble polymer, and by defining the island component arrangement in the islands-in-sea composite fiber (single filament), productivity has been enhanced. A method for manufacturing a fiber has been disclosed (Patent Documents 1 and 2).

Further, a method for producing nanofibers with high strength and excellent abrasion resistance and abrasion resistance is disclosed by specifying the number of islands and the fineness of the single yarn of the sea-island composite fiber (single yarn) (Patent Document 3). ).
In particular, with regard to general-purpose polyesters and nylons with good spinning stability, nanofibers have been put to practical use by the production methods described above, and are being used in clothing fabrics, artificial leathers, filters, and the like.

On the other hand, early research, development, and stable production of ultrafine fibers are also required for high-performance engineering plastics that are used in harsh environments that require heat resistance, chemical resistance, flame resistance, electrical insulation, etc. It is

For example, polyphenylene sulfide (hereinafter also referred to as "PPS") fibers, which are excellent in heat resistance and chemical resistance, are used as filter media for bag filters. As a result, it is expected to be used not only for bag filters, but also for applications such as electrical insulation, papermaking canvas, and battery separators. In these various filter applications, if the thickness is increased, the pressure loss when the fluid passes through will be excessive, and the efficiency of the energy required for filtration will be greatly reduced. is demanded.

In general, PPS fibers are inferior in spinning stability to general-purpose polyesters and nylons, and it is difficult to produce ultrafine fibers. , discloses an example using PPS pulp obtained by beating PPS fibers, but PPS is easily pulverized even if it is beaten, and in practice it is difficult to fully beat PPS fibers.

The publication also discloses split fibers and PPS ultrafine yarns obtained by melt blowing, but the fiber diameter of the single fibers is about 5 μm at most. ) proposes to obtain ultra-fine yarn by so-called sea-island composite fiber. The fineness was insufficient to obtain good PPS microfibers suitable for processing.
Also known are US Pat.

However, with the PPS nanofibers obtained here, it was not easy to uniformly dissolve and remove the sea component up to the center of the thick tow made of polymer alloy fibers. That is, it has been a major technical challenge to obtain a tow that is uniformly nanofiberized to the inside by allowing the deseaing solvent to uniformly permeate the inside of the tow and uniformly discharging the eluted components to the outside of the tow. .

For this reason, it was only possible to obtain PPS nanofibers with non-uniform fiber diameters and with a large amount of fluff, which were inferior in quality and grade.

In this way, in the conventional method, resins such as PPS, which are inferior in spinning stability compared to general-purpose polyester and nylon, are made into ultrafine fibers, and ultrafine fibers with excellent quality and grade with little fluff are stably produced. It was impossible to manufacture

JP 2007-100243 A JP 2007-100253 A JP 2011-208326 A JP-A-2002-279958 JP-A-2-99658 JP-A-2004-169261 JP 2006-257618 A

The problem of the present invention is to solve the problems in the above background art, and for PPS, which is inferior in spinning stability compared to general-purpose polyester and nylon, it has the excellent properties inherent to resins such as high strength and low shrinkage, and fluff To provide an islands-in-the-sea composite fiber bundle capable of stably producing a group of ultrafine fibers having excellent quality and grade with little occurrence of .

The present inventors have completed the present invention as a result of intensive studies to solve the above problems. That is, according to the present invention, there is provided a fiber bundle composed of islands-in-sea composite fibers in which the sea component is a readily soluble polymer and the island component is polyphenylene sulfide. An islands-in-the-sea composite fiber having a diameter of 0.1 to 5.0 μm, a single filament count of the islands-in-the-sea composite fiber of 4 to 48 filaments, and simultaneously satisfying the following requirements (A) to (F): you get a bundle.
(A) The island component polyphenylene sulfide has a melt viscosity of 1000 to 2000 poise at 300° C. and a shear rate of 300 sec ⁻¹ .
(B) The ratio ηa/ηb of the melt viscosity ηa at a temperature of 300° C. and a shear rate of 300 sec ⁻¹ to the melt viscosity ηb at a temperature of 300° C. and a shear rate of 100 sec ⁻¹ of the island component polyphenylene sulfide is 0.8 or more. is.
(C) The number of islands present in the sea-island composite fiber is 10 or more.
(D) The sea-island type composite fiber has a fineness of 6.0 dtex or less.
(E) The strength of the islands-in-the-sea composite fiber is 2 cN/dtex or more.
(F) The strength of the ultrafine fiber composed of the island component obtained by dissolving and removing the sea component of the sea-island composite fiber is 3 cN/dtex or more.

According to the present invention, it is possible to provide a sea-island type composite fiber bundle with excellent spinning stability, and by using this as a raw material, it is suitable for various fields such as bag filters, battery separators, etc., which have both fineness, strength, and uniformity. It is possible to provide a polyphenylene sulfide ultrafine fiber group that can be used for

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, embodiments of the present invention will be described in detail.

PPS applied to the present invention means a polymer having phenylene sulfide units such as p-phenylene sulfide units and m-phenylene sulfide units as repeating units. PPS may be a homopolymer comprising either p-phenylene sulfide units or m-phenylene sulfide units, or may be a copolymer comprising both.
In addition, other aromatic sulfides may be copolymerized within the range in which the effects of the present invention can be obtained.

In the sea-island composite fiber bundle of the present invention, the diameter of the island component in the cross section of the sea-island composite fiber must be 0.1 to 5 μm. If the diameter of the island component is less than 0.1 μm, the PPS fiber structure itself becomes unstable, and the physical properties and fiber morphology become unstable, which is not preferable. On the other hand, if the diameter of the island component is 5 μm or more, it becomes difficult to improve the denseness of the nonwoven fabric and reduce the thickness of the nonwoven fabric, which could not be achieved with existing PPS fibers.

In general, the melt viscosity of a polymer depends on the shear rate, and as the shear rate increases, the melt viscosity decreases. The shear rate dependence at that time also depends on the form of the polymer chain. For example, in the case of non-chain polymer chains (poor linearity) such as crosslinked polymers and branched polymers, the melt viscosity is high when the shear rate is low, but when the shear rate is increased, , the melt viscosity shows a sharp decrease behavior, which is characterized by a large shear rate dependence.

On the other hand, when the shear rate is low, the melt viscosity of polymer chains with good linearity is not as high as in the case of non-linear polymer chains. It is characterized by a small shear rate dependency that does not increase so much.

By the way, since polyphenylene sulfide polymers are not necessarily only polymers with good linearity, it is extremely important to control the melt viscosity within a very limited range in consideration of the above characteristics when making them ultrafine. It's coming. In this respect, the present inventors have found that, in the case of polyphenylene sulfide, the ratio ηa/ηb between the melt viscosity ^ηa at 300°C and a shear rate of 300 sec ^-1 and the melt viscosity ηb at 300°C and a shear rate of 100 sec-1 is 0.8 or more. is preferable in terms of linearity, and it has been found that the use of such a polymer enables nano-order ultra-thin polyphenylene sulfide polymer, which has been difficult in the prior art.

That is, when the ratio of the melt viscosities is less than 0.8, the polyphenylene sulfide ultrafine fibers obtained after dissolving and removing the sea component of the sea-island composite fiber bundle are weak in strength and non-uniform. Polyphenylene sulfide ultrafine fibers cannot be obtained because, in this case, the linearity of the polymer chains is not good, so the elongation at the time of spinning is poor, and the physical properties are sufficient even when the sea component is sufficiently oriented. It is not possible to obtain a product, the stretchability is poor, and there are problems such as frequent yarn breakage and fluff.

Furthermore, the island component polyphenylene sulfide of the present invention has a melt viscosity ηc of 700 to 1200 poise at a temperature of 320° C. and a shear rate of 1000 sec ⁻¹ , and a melt viscosity ηd of 700 to 1200 poise at a temperature of 320° C. and a shear rate of 3000 sec ⁻¹ . is 600 poise or more, and the melt viscosity difference (ηc-ηd) between ηc and ηd is preferably 200 poise or less.

When the melt viscosity ηc at a temperature of 320° C. and a shear rate of 1000 sec ⁻¹ is less than 700 poise, the degree of polymerization is too low and sufficient physical properties, especially strength, cannot be obtained. Many threads. On the other hand, when the melt viscosity ηc exceeds 1200 poise, the degree of polymerization is too high, and the spinning temperature must be increased more than necessary, which accelerates the deterioration of the polymer used as the sea component, resulting in a sea-island composite. It is not preferable because the fiber bundle breaks and fuzz occurs frequently.

Next, the value of the melt viscosity ηd at a temperature of 320° C. and a shear rate of 3000 sec ⁻¹ must be 600 poise or more due to the degree of polymerization and linearity. When the poise is less than 600 poise, the degree of polymerization is extremely low or the linearity is extremely poor, so that the polyphenylene sulfide ultrafine fibers obtained after dissolving and removing the sea component of the islands-in-sea type composite fiber bundle have low strength and unevenness. becomes.

The polyphenylene sulfide used in the present invention can be obtained by a known synthesis method, for example, by reacting anhydrous sodium sulfide with a multihalo-substituted cyclic compound in a polar organic solvent. In order to satisfy the above, it is important to appropriately adjust the polymerization temperature and the polymerization time as shown in the examples below.

Next, the sea component polymer used in the sea-island composite fiber of the present invention can be appropriately selected as long as it is a combination having higher solubility than the island component polymer. For example, polylactic acid, ultra-high-molecular-weight polyalkylene oxide condensed polymer, and copolyester of 5-sodium sulfoisophthalic acid are most suitable as polymers that are readily soluble in an alkaline aqueous solution. Here, the alkaline aqueous solution refers to potassium hydroxide, sodium hydroxide aqueous solution, and the like. Also, nylon 6 is easily dissolved in formic acid, and polystyrene is easily dissolved in organic solvents such as toluene.

In the islands-in-the-sea composite fiber of the present invention, the copolymer polyester of the polyethylene glycol compound and 5-sodium sulfoisophthalic acid contains 6 to 12 mol% of 5-sodium sulfonic acid and 3 to 10% by weight of molecular weight of 4000 to 4,000. It is preferably selected from polyethylene terephthalate copolymers copolymerized with polyethylene glycol of 12,000. It combines into a sea-island type and is discharged. Since the spinning temperature in the final spinneret is the same as that of PPS, the intrinsic viscosity of the sea component polymer is preferably designed to be 0.35 dl/g or more.

It is important that the number of monofilaments of the islands-in-the-sea composite fibers in the islands-in-the-sea composite fiber bundle is 4 to 48 filaments.

If the number of filaments is more than 48 filaments, minute cooling spots, stretching spots, etc. occur between the single yarns, and physical property differences and fineness unevenness occur in the ultrafine single yarn group after the sea component is dissolved and removed. On the other hand, if the number of filaments is less than 4 filaments, the unevenness between the single yarns is small, but even if the sea component is dissolved and removed, a single yarn group consisting of ultrafine single fibers cannot be obtained, and the object of the present invention cannot be achieved. may disappear.

The more the number of islands, the higher the productivity in manufacturing ultrafine single filaments by dissolving and removing the sea component, so 10 or more islands are necessary.

Next, it is important that the sea-island composite fiber (single yarn) has a fineness of 6.0 dtex or less.
If it is 6.0 dtex or less, there is little difference in the degree of cooling and orientation at the surface/core of the sea-island composite fiber (single filament). Yarn groups can be obtained. Furthermore, in order to obtain a group of ultra-fine single yarns with less variation in fiber diameter and less reduction in strength, it is more preferable that the single yarn fineness is 3.0 dtex or less.

However, in order to maintain spinning stability, the single yarn fineness is preferably 0.3 dtex or more.

If the single filament fineness exceeds 6.0 dtex, a difference in cooling occurs between the surface and the core of the sea-island composite fiber (single filament), resulting in large variations in the quality of the ultrafine single filament group after dissolution treatment, which is not preferable.

In addition, the more uniform the diameter of each island component in the cross section of the sea-island composite fiber (single filament), the higher the quality and durability of the ultrafine single yarn group obtained by removing the sea component. CV%, which represents the variation in the diameter of the island component, is preferably 0 to 30%. More preferably 0 to 20%, still more preferably 0 to 15%. A low CV% means that there is little variation in the fineness of the ultrafine single yarn.

In addition, the islands-in-the-sea type composite fiber bundle is excellent in yarn spotting (Worcester spots) as a quality. There is an average deviation rate (U%) as an index of uneven thread, and the lower the value, the better the uneven thread. The average deviation rate is preferably 1% or less, more preferably 0.9% or less, and still more preferably 0.8% or less, measured with a Wooster tester UT-5 manufactured by Zellweger Wooster in half inert mode. and most preferably 0.7% or less.

The ultrafine fiber group composed of island components obtained by dissolving and removing the sea component of the sea-island composite fiber bundle of the present invention has a nano-level fiber diameter with little variation, and can be designed according to the application. For example, in filter applications, if a substance that can be adsorbed by nanofiber single fiber diameter is selected, it becomes possible to design the fiber diameter according to the application, and product design can be carried out very efficiently. become.

Here, as the spinning equipment for producing the sea-island type composite fiber bundle of the present invention, the existing equipment used for polyester can be used as it is, as long as it is capable of high-temperature spinning at a spinning temperature of about 300 to 350 ° C. Available.

The sea component and the island component are melted separately, combined into a sea-island shape in the die, and discharged. The islands-in-the-sea composite fiber discharged from the spinneret passes through a heating zone having a heating length under the spinneret of 30 to 200 mm and an ambient temperature of 250 to 500° C., and a cooling device provided continuously to the heating zone. and then wound up at a spinning speed of 400 to 3000 m/min after being oiled. Here, in order to obtain the islands-in-the-sea composite fiber bundle of the present invention, it is preferable to pass through a heating zone having a heating length under the spinneret of 30 to 200 mm and an ambient temperature of 250°C to 500°C. If there is no heating area, or if the heating length below the spinneret is shorter than 30 mm, the fiber may break during the spinning process, lack strength, and cause uneven fineness and uneven strength between single fibers of the sea-island composite fiber. CV%, which indicates the dispersion of the diameter of the island component, exceeds 30%. If the heating length under the spinneret exceeds 200 mm, the islands-in-the-sea type composite fiber will have fineness unevenness in the yarn length direction. If the temperature of the heating zone below the spinneret is less than 250° C., the strength of the islands-in-the-sea composite fiber bundle is likely to be insufficient, or unevenness in strength or fineness is likely to occur between single fibers. On the other hand, when the temperature exceeds 500° C., unevenness in fineness occurs in the yarn length direction, which is not preferable.

A more preferred range of spinning speed is 600 to 2000 m/min. A spinning speed of less than 200 m/min results in poor productivity, and a spinning speed of more than 3000 m/min results in poor spinning stability.

The obtained sea-island type composite fiber undrawn yarn (bundle) is wound once, and drawn and heat-set in a separate drawing process to obtain a composite fiber bundle having desired strength and elongation, heat shrinkage properties, etc., or It is possible to apply any of the methods in which the fiber is pulled onto a roller at a constant speed without being wound once, then subjected to a drawing process and then wound up to obtain a composite fiber bundle having desired strength and elongation, heat shrinkage properties, etc. .

Specifically, the undrawn yarn (bundle) is preheated on a preheating roller at 60 to 190° C., preferably 75 to 180° C., and the draw ratio is 1.2 to 6.0, preferably 2.0 to It is preferable to stretch the film by a factor of 5.0 and perform heat setting with set rollers at 120 to 220°C, preferably 130 to 200°C. If the preheating temperature is insufficient, the intended high-ratio stretching cannot be achieved. If the set temperature is too low, the shrinkage rate is too high, which is not preferable. On the other hand, if the set temperature is too high, the physical properties of the fiber bundle are significantly lowered, which is not preferable.

In order to dissolve and remove the sea component of the obtained sea-island composite fibers to form ultrafine fibers, any method can be employed as long as the sea component is selectively dissolved in a liquid capable of dissolving and removing the sea component polymer. .

The sea component is a polyethylene terephthalate-based copolymer polyester having an intrinsic viscosity of 0.3 to 0.6 obtained by copolymerizing 6 to 12 mol% of 5-sodium sulfoisophthalic acid and 1 to 5% by weight of polyethylene glycol having a molecular weight of 4,000 to 20,000. , it is preferable to dissolve and remove the sea component in an alkaline aqueous solution having a sodium hydroxide (NaOH) concentration of 1 to 10% by weight at a temperature of 80 to 105°C.

The fiber structure using ultrafine fibers composed of island components obtained by dissolving and removing the sea component of the sea-island composite fiber of the present invention can be used not only in fabrics, but also in cotton, band, string, and thread. Objects, etc. may have any structure or shape. Woven fabrics, knitted fabrics, and non-woven fabrics may be composite materials obtained by blending, blending, interweaving, or interknitting a plurality of types of fibers. Also, these textile products may be used.

Examples of the fiber structure include environmental and industrial material applications such as filters, hazardous substance removal products, and battery separators.

EXAMPLES The present invention will be described in more detail below with reference to Examples and Comparative Examples, but the present invention is not limited to these. Each evaluation item shown in each example is a value measured by the following method.

(1) Melt viscosity The polymer after drying is set in an orifice set to the Ruder melting temperature at the time of spinning and held melted for 5 minutes. plot. The plots were smoothly connected to create a shear rate-melt viscosity curve, and the melt viscosities of a) to d) were read below.
a) Temperature 300°C, shear rate 100 sec ^-1
b) Temperature 300°C, shear rate 300 sec ^-1
c) Temperature 320°C, shear rate 1000 sec ^-1
d) Temperature 320°C, shear rate 3000 sec ^-1

(2) Intrinsic Viscosity The intrinsic viscosity [η] of the chip was measured at a concentration of 1.2 g/100 ml in an o-chlorophenol solution and at a temperature of 35°C.

(3) Strength and elongation of islands-in-the-sea composite fiber Measured according to JIS-L1017, using Autograph AGS500D manufactured by Shimadzu Corporation, at a sample length of 100 mm and a tensile speed of 100 mm/min.

(4) Strength and elongation of ultrafine fibers
A tubular knitted fabric having a weight of 1 g or more was produced using the islands-in-the-sea composite fiber, and the knitted fabric was treated with a solvent to remove the sea component. A knitted fabric composed of the obtained ultrafine fibers was unwound, and a load-elongation curve chart of the obtained ultrafine fibers was prepared under the conditions of room temperature, initial sample length = 100 mm, and tensile speed = 200 m/min. The strength (cN/dtex) and elongation (%) of the ultrafine fibers were obtained from the above chart.

(5) Number of islands and ratio of sea component/island component in cross section of sea-island composite fiber (single filament) observed and measured.

(6) Diameter of Island Component in Cross Section of Sea-island Composite Fiber (Single Filament) The island component was observed from a cross-sectional photograph of the sea-island composite fiber (single filament) taken at a magnification of 30000 times with a transmission electron microscope TEM. The average value of the major axis and the minor axis was taken as the diameter. 50 island components were randomly observed, and the average island component diameter (r) was calculated.

(7) Variation CV% of mean island component diameter
When obtaining the average island component diameter (r), its standard deviation σ was calculated, and the island component diameter variation coefficient CV% defined below was calculated.
CV% = standard deviation σ/average island component diameter r × 100 (%)

(8) Thread spots in the longitudinal direction (Worcester spots)
Using a Wooster Tester UT-5 manufactured by Zellweger Wooster Co., Ltd., the average deviation rate (U%) of the islands-in-the-sea composite fiber bundle was measured in half inert mode.
Yarn feeding speed: 400m/min Measured yarn length: 2000m
If the U% value was less than 1.0, it was judged to be a sea-island type composite fiber bundle with little yarn unevenness.

(9) Spinning Stability Spinning was performed for each example, and the case where continuous spinning was possible for 7 hours or more without yarn breakage was evaluated as "good", and the other cases were evaluated as "bad".

(10) Fluff The appearance of the wound sea-island type composite fiber bundle was examined, and evaluated and displayed as "good" when fluff was hardly found, and as "poor" when fluff could be easily found.
A. Polymer synthesis
(a) In Table 1 below, 95.4 g of the polymer sodium sulfide used in Examples 1 to 3 and Comparative Example 3, 76.5 g of lithium acetate dihydrate, 185 g of NMP (N-methylpyrrolidone), and 14 g of water were A glass flask was charged and treated at 210° C. for 2 hours to produce 44 CC of distillate. Next, a solution of 80 g of NMP and 225 g of DCB (dichlorobenzene) was added and heated at 260° C. for 5 hours under a nitrogen seal (pressure 5 kg/cm ³ ).
The product was then washed ten times with hot water, dried and chipped.
Melt viscosity characteristics were as follows.
a) Temperature 300°C, shear rate 100 sec ^-1 : 1860 poise b) Temperature 300 °C, shear rate 300 sec ^-1 : 1730 poise c) Temperature 320 °C, shear rate 1000 sec ^-1 : 970 poise D) Temperature 320 °C, shear rate 3000 sec ⁻¹ : 820 poise The obtained chips were dried in a hot air dryer at 180° C. for 4 hours and used for yarn production evaluation.
(b) Synthesis of Polymers Used in Comparative Examples 1 and 2 in Table 1 below Polymers were obtained in the same manner as in the synthesis method (a) except that the polymerization time was changed to 3 hours.
Melt viscosity characteristics were as follows.
a) Temperature 300°C, shear rate 100 sec ^-1 : 1560 poise b) Temperature 300°C, shear rate 300 sec ^-1 : 1230 poise c) Temperature 320°C, shear rate 1000 sec ^-1 : 620 poise d) Temperature 320°C, shear rate 3000 sec ⁻¹ : 480 poise The obtained chips were dried in a hot air dryer at 180° C. for 4 hours and used for yarn production evaluation.
B. Spinning (spinning, drawing)

[Example 1]
Polyphenylene sulfide obtained in A-(a) as the island component, and polyethylene having an intrinsic viscosity of 0.39 obtained by copolymerizing 9 mol% of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4000 as the sea component. Terephthalate (referred to as modified PET1) was used.

After melting the island component and the sea-island component separately, polyphenylene sulfide at 340°C and polyethylene terephthalate at 280°C, spinning for manufacturing a sea-island composite fiber having 24 ejection holes with a hole diameter of 0.25 mm and a land length of 0.6 mm. They were combined in a spinneret, and a sea-island composite undrawn yarn with islands:sea=70:30 (weight ratio) and number of islands=12 was discharged at a spinning temperature of 320.degree. After that, it passed through a heating zone under the spinneret with a heating length of 90 mm and an atmospheric temperature of 400° C., passed through a cooling device continuously provided in the heating zone, was then oiled, and was wound at a spinning speed of 1000 m/min. .

The undrawn yarn was adjusted in the spinning flow rate and the draw ratio so that the yarn count of the drawn and heat-treated sea-island composite fiber bundle was 56 dtex/24 filaments. Tables 1 and 2 show the evaluation results of the sea-island composite fiber bundles obtained.

[Example 2]
Using the same sea-island polymer as in Example 1, after separately melting the sea component and the island component, a spinneret for manufacturing a sea-island composite fiber having six discharge holes with a hole diameter of 0.3 mm and a land length of 0.6 mm was used. , and a sea-island composite undrawn fiber with islands:sea=70:30 (weight ratio) and number of islands=90 was discharged at a spinning temperature of 320.degree. After that, the fiber was passed through a heating zone under the spinneret with a heating length of 90 mm and an atmospheric temperature of 450°C, then through a cooling device continuously provided in the heating zone, then oiled, and then wound at a spinning speed of 1000 m/min. .

The spinning discharge flow rate and draw ratio of the undrawn yarn were adjusted so that the yarn count of the drawn and heat-treated sea-island composite fiber bundle was 36 dtex/6 filaments. Tables 1 and 2 show the evaluation results of the sea-island composite fiber bundles obtained.

[Example 3]
Using the same sea-island polymer as in Example 1, after separately melting the sea component and the island component, a spinneret for manufacturing a sea-island composite fiber having 16 ejection holes with a hole diameter of 0.2 mm and a land length of 0.6 mm was used. , and a sea-island composite undrawn fiber having islands:sea=70:30 (weight ratio) and number of islands=720 was discharged at a spinning temperature of 320.degree. After that, the fiber was passed through a heating zone under the spinneret with a heating length of 90 mm and an atmospheric temperature of 450°C, then through a cooling device continuously provided in the heating zone, then oiled, and then wound at a spinning speed of 1000 m/min. .

The spinning discharge flow rate and the draw ratio of the undrawn yarn were adjusted so that the yarn count of the drawn and heat-treated sea-island composite fiber bundle was 56 dtex/16 filaments. Tables 1 and 2 show the evaluation results of the sea-island composite fiber bundles obtained.

[Comparative Example 1]
9 mol % of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4000 were used as the sea component in the same manner as in Example 1, except that the polyphenylene sulfide obtained in A-(b) was used as the island component. was copolymerized and had an intrinsic viscosity of 0.39 (referred to as modified PET1). After melting the island component and the sea-island component separately, polyphenylene sulfide at 340°C and polyethylene terephthalate at 280°C, spinning for manufacturing a sea-island composite fiber having 24 ejection holes with a hole diameter of 0.25 mm and a land length of 0.6 mm. They were combined in a spinneret, and a sea-island composite undrawn yarn with islands:sea=70:30 (weight ratio) and number of islands=12 was discharged at a spinning temperature of 320.degree. After that, it passed through a heating zone under the spinneret with a heating length of 90 mm and an atmospheric temperature of 400° C., passed through a cooling device continuously provided in the heating zone, was then oiled, and was wound at a spinning speed of 1000 m/min. .

The spinning discharge flow rate and draw ratio of the undrawn yarn were adjusted so that the yarn count of the drawn and heat-treated sea-island composite fiber bundle was 56 dtex/24 filaments. Tables 1 and 2 show the evaluation results of the sea-island composite fiber bundles obtained.

A sea-island type composite fiber bundle was obtained without breaking the yarn, but due to the lack of linearity of the PPS, the strength was low, the island component diameter varied greatly, and there was a lot of fluff. It was not suitable for the purpose of

[Comparative Example 2]
9 mol % of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4000 were used as the sea component in the same manner as in Example 2, except that the polyphenylene sulfide obtained in A-(b) was used as the island component. was copolymerized and had an intrinsic viscosity of 0.39 (referred to as modified PET1). After melting the island component and the sea-island component separately, polyphenylene sulfide at 340°C and polyethylene terephthalate at 280°C, spinning for producing a sea-island type composite fiber having 6 ejection holes with a hole diameter of 0.3 mm and a land length of 0.6 mm. The fibers were combined in a spinneret, and a sea-island composite undrawn fiber having an island:sea ratio of 70:30 (weight ratio) and the number of islands of 90 was discharged at a spinning temperature of 320°C. After that, the fiber was passed through a heating zone under the spinneret with a heating length of 90 mm and an atmospheric temperature of 450°C, then through a cooling device continuously provided in the heating zone, then oiled, and then wound at a spinning speed of 1000 m/min. .

The spinning discharge flow rate and draw ratio of the undrawn yarn were adjusted so that the yarn count of the drawn and heat-treated sea-island composite fiber bundle was 36 dtex/6 filaments. Tables 1 and 2 show the evaluation results of the sea-island composite fiber bundles obtained.

Many yarn breakage occurred during the conjugate spinning stage, making continuous yarn spinning impossible. Since there was a large variation in component diameter and there was a large amount of fluff, it was not suitable for the intended use.

[Comparative Example 3]
Polyphenylene sulfide obtained in A-(a) as the island component, and polyethylene having an intrinsic viscosity of 0.39 obtained by copolymerizing 9 mol% of 5-sodium sulfoisophthalic acid and 3% by weight of polyethylene glycol having a number average molecular weight of 4000 as the sea component. Terephthalate (referred to as modified PET1) was used. After melting the island component and the sea-island component separately, polyphenylene sulfide at 340°C and polyethylene terephthalate at 280°C, spinning for producing a sea-island composite fiber having 10 ejection holes with a hole diameter of 0.35 mm and a land length of 0.7 mm. They were combined in a spinneret, and a sea-island composite undrawn yarn with islands:sea=70:30 (weight ratio) and number of islands=12 was discharged at a spinning temperature of 320.degree. After that, it passed through a heating zone under the spinneret with a heating length of 90 mm and an atmospheric temperature of 400° C., passed through a cooling device continuously provided in the heating zone, was then oiled, and was wound at a spinning speed of 1000 m/min. .

The spinning discharge flow rate and draw ratio of the undrawn yarn were adjusted so that the yarn count of the drawn and heat-treated sea-island composite fiber bundle was 80 dtex/10 filaments. Tables 1 and 2 show the evaluation results of the sea-island composite fiber bundles obtained.

Since PPS with good linearity was used in the same manner as in the Examples, a sea-island composite fiber bundle could be obtained. / Due to the difference in the degree of cooling and the degree of orientation at the core, the island component diameter varied greatly and the Worcester spots were also poor. In addition, since there is a lot of fluff, it is not suitable for the purpose of this application.

The ultrafine fiber of the present invention can be used for environmental and industrial material applications such as filters, hazardous substance removal products and battery separators, and for medical applications such as artificial blood vessels and blood filters.

Claims (5)

A fiber bundle composed of islands-in-sea composite fibers in which the sea component is a readily soluble polymer and the island component is polyphenylene sulfide, wherein the diameter of the island component in the cross section of the sea-island composite fiber is 0.1 to 5.5. 0 μm, the number of single filaments of the islands-in-sea composite fiber is 4 to 48 filaments, and the following requirements (A) to (F) are simultaneously satisfied.
(A) The island component polyphenylene sulfide has a melt viscosity of 1000 to 2000 poise at 300° C. and a shear rate of 300 sec ⁻¹ .
(B) The ratio ηa/ηb of the melt viscosity ηa at a temperature of 300° C. and a shear rate of 300 sec ⁻¹ to the melt viscosity ηb at a temperature of 300° C. and a shear rate of 100 sec ⁻¹ of the island component polyphenylene sulfide is 0.8 or more. is.
(C) The number of islands present in the sea-island composite fiber is 10 or more.
(D) The sea-island type composite fiber has a fineness of 6.0 dtex or less.
(E) The strength of the islands-in-the-sea composite fiber is 2 cN/dtex or more.
(F) The strength of the ultrafine fiber composed of the island component obtained by dissolving and removing the sea component of the sea-island composite fiber is 3 cN/dtex or more. The island component polyphenylene sulfide has a melt viscosity ηc of 700 to 1200 poise at a temperature of 320° C. and a shear rate of 1000 sec ⁻¹ , and a melt viscosity ηd of 600 poise or more at a temperature of 320° C. and a shear rate of 3000 sec ⁻¹ , 2. The islands-in-the-sea composite fiber bundle according to claim 1, wherein the melt viscosity difference (ηc-ηd) between ηc and ηd is 200 poise or less. 3. The islands-in-the-sea composite fiber bundle according to claim 1, wherein CV%, which indicates the variation in the diameter of the island component in the cross section of the islands-in-the-sea composite fiber, is 0 to 30%. The islands-in-the-sea composite fiber bundle according to any one of claims 1 to 3, having a U% of 1.0 or less as measured in half inert mode with a Wooster tester UT-5 manufactured by Zellweger Wooster. The sea-island composite fiber bundle according to any one of claims 1 to 4, wherein the easily soluble polymer used for the sea component has an intrinsic viscosity of 0.35 dl/g or more.